Wis. Stat. § 941.298: Firearm silencers.

(1) In this section, “firearm silencer” means any device for silencing, muffling or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for use in assembling or fabricating such a device, and any part intended only for use in that assembly or fabrication.

(2) Whoever sells, delivers or possesses a firearm silencer is guilty of a Class H felony.

(3) Subsection (2) does not apply to sales or deliveries of firearm silencers to or possession of firearm silencers by any of the following:

(a) Any peace officer who is acting in compliance with the written policies of the officer’s department or agency. This paragraph does not apply to any officer whose department or agency does not have such a policy. Notwithstanding s. 939.22 (22), this paragraph does not apply to a commission warden.

(b) Any armed forces or national guard personnel, while in the line of duty.

(c) Any person who has complied with the licensing and registration requirements under 26 USC 5801 to 5872.